Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2003
Publication Date: 4/1/2004
Citation: Mater, Y., Baenziger, P.S., Gill, K., Graybosch, R.A., Whitcher, L.C., Baker, C.A., Specht, J., Dweikat, I. 2004. Linkage mapping of powdery mildew and greenbug resistance genes on recombinant 1rs from amigo and kavkaz wheat-rye translocations of chromosome 1rs.1al.. Genome. 47:292-298.
Interpretive Summary: Wheat breeders have been introducing alien genetic materials from wild and cultivated relatives of wheat since the 1930¿s. Wide hybrids, with or without embryo rescue, have been used to introduce useful genetic materials from a host of relatives, including various goat grasses, wheat grasses, and, most importantly, cultivated rye. In the U.S., approximately 15% of the currently grown wheat cultivars contain ½ of a rye chromosome, either attached to wheat chromosome 1A or 1B. These rye chromosomes carry genes for resistance to several fungal pathogens and insect pests, and provide enhanced grain yield under conditions of abiotic stress. Unfortunately, the rye chromosomes also carry genes that diminish processing quality, especially in bread making operations. To counter these deleterious effects, it would be useful to genetically separate the useful from the non-useful genes. The rye chromosomes will recombine with wheat chromosomes, and exchange genetic materials, but only in certain mutant backgrounds. This is a rather laborious task, and the chance for success depends upon the distance of the useful from the non-useful genes. This study was designed to map these genetic distances. Unfortunately, the disease resistance genes were found to be tightly linked to the negative storage protein genes. To genetically separate the two traits, breeders will need to evaluate several hundred progeny for each mating in the mutant backgrounds.
Technical Abstract: Cultivated rye (Secale cereale L., 2n = 2x = 14, RR) is an important source of genes for insect and disease resistance in wheat (Triticum aestivum L., 2n=6x=42). Rye chromosome arm IRS of the 'Kavkaz' that was originally found as a 1BLIRS translocation, carries genes for disease resistance (e.g. Lr26 , Sr31, Yr9, and Pm8), while IRS of the 'Amigo' translocation (IRS A) carries a single resistance gene for greenbug (Schizaphis graminum Rondani) biotype B and C and also carries additional disease resistance genes. The purpose of this research was to identify individual plants that were recombinant in the homologous region of.IAL.1RSv and IAL.IRSA using both molecular and phenotypic markers. Nekota (1 AL. I RSA) and Pavon 76 (I AL.1 RSv) were mated and the F 1 was backcrossed to Nekota (IAL.IAS) to generate eighty BCIF2 families [i.e., (Nekota IAL.1RSA X Pavon 76 lAL.IRSv) X Nekota IAL.IAS]. These families were genotyped using the secalin-gliadin grain storage protein banding pattern generated with polyacrylamide-gel electrophoresig to discriminate IAL.IAS/IAL.1RS heterozygotes from the IAL.1RSA+v and IAL.IAS homozygotes. Segregation of the secalin locus and PCR markers based on the R173 family of rye specific repeated DNA sequences demonstrated the presence of recombinant IAL.1RSA+v families. Powdery mildew (Blumeria graminis) and greenbug resistance genes on the recombinant IRS A+v arm were mapped in relation to the Sec-1 locus, two additional protein bands, three SSRs and 13 RFLP markers. The resultant linkage map of IRS spanned 82.4 cM with marker order and spacing showing reasonable agreement with previous maps of IRS. Fifteen markers lie within a region of 29.7 cM next to the centromere, yet corresponded to just 36% of the overall map length. The map position of the RFLP marker probe mwg68 was 10.9 cM distal to the Sec-1 locus and 7.8 cM proximal to the powdery mildew resistance locus. The greenbug resistance gene was located 2.7 cM proximal to the Sec-1 locus.